It is known to measure the forward and reflected power at the aerial of a radio transmitter and to provide the operator with an indication of the appropriate values. However, it has been necessary to use either two separate displays to distinguish between forward and reflected power or to provide a single display. and a switch for enabling an operator to switch the display between indications of forward and reflected power. These known methods therefore make it relatively difficult for an operator to obtain full information concerning the operational status of the radio, antenna tuner and antenna system in a convenient and self explanatory manner.
Furthermore, when the output includes a voice signal, the RF power envelope corresponding to the voice signal has maxima at syllables and minima at intervals between syllables or between words. Rapid changes in the peak envelope power can cause rapid changes in the display of the power value and this can make it difficult for the operator to see and/or understand the display.